Build the vertical based scrollable view controller.

xingheng · May 4, 2020 · e20406f · e20406f
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diff --git a/DSBaseViewController/ScrollableViewController.h b/DSBaseViewController/ScrollableViewController.h
@@ -0,0 +1,30 @@
+//
+//  ScrollableViewController.h
+//  DragonSourceCommon
+//
+//  Created by WeiHan on 1/28/16.
+//  Copyright © 2016 DragonSource. All rights reserved.
+//
+
+#import "DSBaseViewController.h"
+
+@interface ScrollableViewController : DSBaseViewController
+
+/// The root view of view controller.
+@property (nonatomic, strong, readonly) UIScrollView *scrollView;
+
+/// The container view which all the subviews should be added to.
+@property (nonatomic, strong, readonly) UIView *containerView;
+
+/// The content inset between scrollView and containerView, defaults to UIEdgeInsetsZero.
+@property (nonatomic, assign) UIEdgeInsets contentInset;
+
+/// With autolayout, the subclass should give a valid view to lastBottomView which is used for layout children views within scroll view.
+@property (nonatomic, strong) UIView *lastBottomView;
+
+/// keyboard frame notification
+///
+/// CGRect values are converted to current root view's coordinates.
+@property (nonatomic, copy) void (^ keyboardChangedBlock)(CGRect beginRect, CGRect endRect);
+
+@end
diff --git a/DSBaseViewController/ScrollableViewController.m b/DSBaseViewController/ScrollableViewController.m
@@ -0,0 +1,159 @@
+//
+//  ScrollableViewController.m
+//  DragonSourceCommon
+//
+//  Created by WeiHan on 1/28/16.
+//  Copyright © 2016 DragonSource. All rights reserved.
+//
+
+#import "ScrollableViewController.h"
+
+@interface ScrollableViewController ()
+
+@property (nonatomic, strong) UIView *containerView;
+
+@property (nonatomic, strong) NSMutableArray<NSLayoutConstraint *> *containerViewEdgeConstraints;
+@property (nonatomic, strong) NSLayoutConstraint *containerViewBottomConstraint;
+@property (nonatomic, strong) NSLayoutConstraint *containerViewHeightConstraint;
+
+@end
+
+@implementation ScrollableViewController
+
+- (void)loadView
+{
+    UIScrollView *scrollView = [UIScrollView new];
+    UIView *containerView = [UIView new];
+
+    if (@available(iOS 11.0, *)) {
+        scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
+    } else {
+        self.automaticallyAdjustsScrollViewInsets = NO;
+    }
+
+    containerView.translatesAutoresizingMaskIntoConstraints = NO;
+
+    self.view = scrollView;
+    self.containerView = containerView;
+    [scrollView addSubview:containerView];
+
+    self.contentInset = UIEdgeInsetsZero;
+}
+
+- (void)updateViewConstraints
+{
+    // Make sure the container's height constraint binds to minimal height
+    //  of scrollView if the bottom constraint isn't ready.
+    if (!self.containerViewBottomConstraint) {
+        self.containerViewHeightConstraint = [NSLayoutConstraint constraintWithItem:self.containerView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:self.scrollView attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0];
+        self.containerViewHeightConstraint.active = YES;
+    }
+
+    [super updateViewConstraints];
+}
+
+- (void)viewDidLoad
+{
+    [super viewDidLoad];
+
+    // Enable the vertical bounce to wake up the scrollable gesture manually.
+    // self.scrollView.alwaysBounceVertical = YES;
+
+    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardFrameWillChange:) name:UIKeyboardWillChangeFrameNotification object:nil];
+}
+
+- (void)didReceiveMemoryWarning
+{
+    [super didReceiveMemoryWarning];
+    // Dispose of any resources that can be recreated.
+}
+
+- (void)dealloc
+{
+    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillChangeFrameNotification object:nil];
+}
+
+#pragma mark - Public
+
+- (void)setLastBottomView:(UIView *)lastBottomView
+{
+    _lastBottomView = lastBottomView;
+    NSParameterAssert(lastBottomView);
+
+    self.containerViewHeightConstraint.active = NO;
+    self.containerViewHeightConstraint = nil;
+
+    if (self.containerViewBottomConstraint) {
+        self.containerViewBottomConstraint.active = NO;
+    }
+
+    self.containerViewBottomConstraint = [NSLayoutConstraint constraintWithItem:self.containerView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:lastBottomView attribute:NSLayoutAttributeBottom multiplier:1.0 constant:self.contentInset.bottom];
+    self.containerViewBottomConstraint.active = YES;
+}
+
+#pragma mark - Property
+
+- (UIScrollView *)scrollView
+{
+    return (UIScrollView *)self.view;
+}
+
+- (void)setContentInset:(UIEdgeInsets)contentInset
+{
+    _contentInset = contentInset;
+
+    if (self.containerViewEdgeConstraints) {
+        [self.containerViewEdgeConstraints enumerateObjectsUsingBlock:^(NSLayoutConstraint *_Nonnull obj, NSUInteger idx, BOOL *_Nonnull stop) {
+            obj.active = NO;
+        }];
+        [self.containerViewEdgeConstraints removeAllObjects];
+    } else {
+        self.containerViewEdgeConstraints = [NSMutableArray new];
+    }
+
+    void (^ MakeEqualConstraint)(id, id, NSLayoutAttribute, CGFloat) = ^(id item1, id item2, NSLayoutAttribute attr, CGFloat constant) {
+        NSLayoutConstraint *constraint =
+            [NSLayoutConstraint constraintWithItem:item1
+                                         attribute:attr
+                                         relatedBy:NSLayoutRelationEqual
+                                            toItem:item2
+                                         attribute:attr
+                                        multiplier:1.0
+                                          constant:constant];
+        constraint.active = YES;
+        [self.containerViewEdgeConstraints addObject:constraint];
+    };
+
+    UIView *scrollView = self.scrollView, *containerView = self.containerView;
+    MakeEqualConstraint(containerView, scrollView, NSLayoutAttributeWidth, -contentInset.left - contentInset.right);
+    MakeEqualConstraint(containerView, scrollView, NSLayoutAttributeTop, contentInset.top);
+    MakeEqualConstraint(containerView, scrollView, NSLayoutAttributeLeft, contentInset.left);
+    MakeEqualConstraint(containerView, scrollView, NSLayoutAttributeBottom, contentInset.bottom);
+    MakeEqualConstraint(containerView, scrollView, NSLayoutAttributeRight, contentInset.right);
+}
+
+#pragma mark - Private
+
+// http://stackoverflow.com/questions/26213681/ios-8-keyboard-hides-my-textview/26226732#26226732
+- (void)keyboardFrameWillChange:(NSNotification *)notification
+{
+    CGRect keyboardEndFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
+    CGRect keyboardBeginFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
+    UIViewAnimationCurve animationCurve = [[[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue];
+    NSTimeInterval animationDuration = [[[notification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey] integerValue];
+
+    [UIView beginAnimations:nil context:nil];
+    [UIView setAnimationDuration:animationDuration];
+    [UIView setAnimationCurve:animationCurve];
+
+    CGRect keyboardFrameEnd = [self.view convertRect:keyboardEndFrame toView:nil];
+    CGRect keyboardFrameBegin = [self.view convertRect:keyboardBeginFrame toView:nil];
+
+    if (self.keyboardChangedBlock) {
+        self.keyboardChangedBlock(keyboardFrameBegin, keyboardFrameEnd);
+    }
+
+    [UIView commitAnimations];
+}
+
+@end